The present invention relates to a semiconductor device and a method of manufacturing the semiconductor device. For example, the invention relates to a semiconductor device having a superjunction structure and a method of manufacturing the semiconductor device.
For a vertical power MOSFET being a power semiconductor device, use of a superjunction structure is investigated to reduce on resistance while a withstand voltage is maintained.
For example, Japanese Unexamined Patent Application Publication No. 2008-305927 discloses a semiconductor device having a PN column layer in which n-conductivity-type columns and p-conductivity-type columns are alternately arranged while being in contact with each other. Japanese Unexamined Patent Application Publication No. 2008-305927 further discloses a technology, in which a trench is formed, the trench being narrow on a silicon substrate side (bottom face side) and wide on an upper opening side, and an embedded epitaxial layer made of silicon having the p conductivity type is formed in the trench such that impurity concentration is distributed to be high on the silicon substrate side (bottom face side) and low on the upper opening side.